The Santa Clarita Diet star, who shares daughters Olive, 6, and Frankie, 4, with ex-husband Will Kopelman, may be trying to slim down after having kids or be wanting to feel better in her own skin - we don't know at this point.

Barrymore doesn't reveal the motivation behind her weight loss in the honest post, but she does admit she feels great about her progress.

Drew started, "When I look at Instagram, I am made to think I should be at my best self, but most days, I lack consistency due to real life.

"Solution: with the right people (@marniealton) we can make our goals a reality...

"Here is me in a before pose and then 25 pounds (11.3kgs) later in the same place."

Drew was noticeably thinner a few months into her fitness journey. Image: Instagram @drewbarrymore

Drew then posted the above image for comparison, and you can certainly see her hard work has been paying off - the Music and Lyrics actress looks incredible!

"You can tell my face is so much thinner!" she continued. "This takes me so much work. Diet and exercise and fighting like a lion for it! Damn you genetics! And yet thank you for all the good stuff.

"I love where I come from (JOHN ETHEL LIONEL) and whatever package it comes in. I just know that I have the control to be what I want. Even if it is hard AF!"

We relate to this so much - losing the last few kilos (or any weight, for that matter) takes a lot of time, resources and effort so we commend Drew for this incredible feat!

But Drew didn't stop there: "At least I know there are experts I can turn to for help. I mean look at what Marnie helped me do in three months!

"When i have time off in 2019...I'm comin for ya! PS may I just say I want to be these ladies on the front page. You are my spirit animals and my goal posts!"

What a difference a few months makes!

Drew with her trainer, Marnie. Image: Instagram @drewbarrymore

We think Drew looks wonderful at any size but it's great to see her so happy! We can't wait to see where Drew's fitness journey takes her in 2019, hopefully she shares some great tips and tricks that we can try!